a) Field of the Invention
The present invention relates to a surface profile detecting device for detecting an uneven surface profile of an object to be measured without contacting the surface based on changes in magnetic flux.
b) Description of the Related Art
Conventionally, a micrometer is one which can precisely measure an uneven surface profile of an object to be measured and is simple and inexpensive. However, since the micrometer performs measurements while the object to be measured is fixed and a probe thereof contacts the uneven surface, it takes time for the procedure. For this reason, it is so difficult to quickly detect the uneven profile of the object surface that the micrometer cannot be used in applications for detecting uneven surface profiles of objects passing in immediate succession, that is, in a coin identifying device built in a vending machine.
For example, in the coin identifying device built in a vending machine, multiple sensors are provided to collect various kinds of information about inserted coins and determine the kinds and legality of the coins. One of the sensors provided in the coin identifying device is an eddy-current sensor. The eddy-current sensor is placed to face a coin passage so that it electrically detects changes in magnetic flux when coins pass by. In other words, a specific resistance varies depending on the material and thickness of the coin, and accordingly the eddy-current loss varies in each coin. The eddy-current sensor electrically detects changes in magnetic flux caused by such an eddy-current loss, and then emits a signal. Therefore, the coin identifying device detects the material, thickness, and diameter of the inserted coin based on the changes in detection outputs of the eddy-current sensor, and also detects data based on detection outputs of other sensors. By comparing those results with the data stored in advance, the kinds and validity of the inserted coin are determined. However, such a coin identifying device is very complex and expensive.
Also, presently coins are forged more precisely, so the coin identifying device built in vending machines is required to determine the kinds and validity of coins based on the complicated and fine, uneven profile on the surfaces of the coins. That is, the development of a simple and inexpensive surface profile detecting device is demanded in which an uneven surface profile of an object to be measured can be detected with no surface contact.
As a method of detecting an uneven surface profile with no surface contact, there are methods in which an image captured by a CCD camera is processed and in which a semiconductor laser is illuminated onto an uneven surface and its reflection is captured by a photodiode. However, in the method of capturing an image in a CCD camera, since an uneven profile is processed as two-dimensional image data, fake coins on which a picture of a valid coin is attached cannot be distinguished. Also, when a light is illuminated with a shallow angle from the periphery to make it easy to optically obtain the information on the uneven profile, if the center portion of the coin is depressed, it is difficult to obtain enough reflection and the center portion becomes dark, and therefore possible to mistakenly recognize the depression as a hole. Also, in the method of capturing the reflection of the semiconductor laser by photodiode, it is necessary to scan all the surface of the coin with a laser beam. In addition, in both of these methods, rust and dirt on the uneven surface differ in each coin, causing a problem with identification. Also, to detect the uneven profile of the coin surface, an additional, expensive device used only for detecting uneven profiles needs to be provided, thus increasing manufacturing cost and enlarging the device. This is not appropriate. Therefore, in the coin identifying device, it is convenient if a conventionally equipped sensor that detects materials is developed to enable the detection of uneven profiles of coin surfaces and then the data on the uneven profiles of coin surfaces, as well as the data on the coin material, is obtained.
The development of such a surface profile detecting device is needed not only for coin identification, but also for other applications.